Drill bit



M-ch'S, 1963 Filed Feb. 27. 1959 J. B. BAKER 3,080,009

DRILL BIT 2 Sheets-Sheet 1 FIG. 2

#Warn/frs.

J. B. BAKER DRILL BIT` March 5, 1963 2 Sheets-Sheet 2 Filed Feb. 27,1959 38 /X 34 Flc-:9

meente Patented Mas'. i963 3,080,099 DRLL BET Kohn B. Baker, Canton,Ghia, assigner to The Timken Roller Bearing Company, Canton, hio, acorporation of @hie Filed Feb. 27, 1959, Ser. No. 795,?54 3 Claims. (Cl.175-410) The present invention relates generally to drill bits and moreparticularly to drill bits having one or more cutting inserts.

It is well known to make drill bits with cutting inserts which `areformed having zones of different hardness. The known inserts, however,have been formed by attaching several dierent .and distinct elements ofdifferent hardness materials together yand then attaching the resultinginsert to the body of a rock drill bit. In the known devices the severalydifferent hardness materials simultaneously contact the material beingdrilled .and their different hardness characteristics cause uneven wearof the materials and fractures. Furthermore, the known devices aredisadvantageous to use because they have distinct fracture zones formedwhere the materials of diiferent hardness meet including the zonebetween the insert `and the drill bit proper. For these and otherreasons the known constructions have been unsatisfactory and haverequired relatively more frequent regrinding and replacement withincident relatively higher drilling costs.

The present invention overcomes these and other disadvantages of theknown devices by providing an insert formed of several materials of`different hardness which are fused together during the forming processby a sintering operation so that there are no distinct fracture zonesbetween materials, and if desired, the insert can also be fused to thedrill bit, thereby also eliminating the formation of distinct fracturezones therebetween also. By so providing, the present insert and bitconstruction incorporate lthe desirable characteristics of all of thedifferent materials used and also greatly reduced the chance offracture. Furthermore, the usable life of a drill bit having insertsconstructed according to this invention is substantially increasedbecause only the most wear resistant material is in contact with thesurface being drilled during `a substantial portion of the life of theinsert and t` is portion of the drill life encompasses the period inwhich maximum cutting efficiency takes place. The present device alsoreduces the regrinding rand maintenace cost of drilling.

it is therefore a principal object of the present invention to increasethe life of drill bits.

Another object is to minimize the chance of fractures in drill bits anddrill bit inserts.

Another object is to provide an insert for a drill bit constructed yofmaterials having different hardness characteristics, which insert hasonly one of the materials thereof in contact with a surface beingdrilled during a substantial portion of its life.

Another object is to provide an insert constructed by fusing togetherseveral materials having different hardness characteristics, said inserthaving predominantly wear resistant characteristics exposed on theworking surfaces thereof.

Another object is to reduce the maintenance costs of rock drills.

Still another object is to provide an insert which incorporates thedesirable characteristics of several different materials.

The present device consists of an insert adapted to be installed on orfused to lthe body of a drill bit, said insert being formed by fusingseveral materials having different hardness and wear characteristicstogether so that during the initial :stages of la drill operation onlyone of the materials is exposed to the surface being drilled.

These and Aother objects and advantages of the present invention willbecome apparent after considering the following detailed specificationin conjunction with the accompanying drawing, wherein:

FIG. l is a side elevational view of Lan insert for a drill bitconstructed according to the teachings of the present invention,

FIG. 2 is a right e-nd view of the insert of FIG. l,

FIG. 3 is a sectional view taken on line 3-3 of FIG. 1,

FfG. 4 is a sectional View taken on line 4-4 of FIG. 2,

FIG. 5 is a side view, partly cut away and sectioned for clarity,showing a modified form of the present insert construction installed ona drill bit,

FIG. 6 is a side View of a drill bit having inserts constructedaccording to this invention.

FiG. 7 is -a fragmentary cross-section view taken on line 7 7 of FIG. 5;

FIG. 8 is a top plan view vof a typical mold structure for making thebit of FIGS. 5--7;

FiG. 9 is a ycross-sectional view of the mold of FiG. 8 taken on line 99 thereof, Iand FIG. l0 is another cross-sectional view of the mold ofFlG. 8 taken `on line lil-lil thereof.

Referring now to the drawing in det-ail yand by reference numbers, thenumber i0 identities generally an insert fora drill bit, such as a rockdrill bit, which is constructed according to the 'teachings of thepresent invention.

The insert 1d' has a cutting edge 12 defined lat the juncture of two.adjacent sloping cutting surfaces 14 and i6. The body of the insert,for illustrative purposes, is shown as having lspaced side surfaces 1Sand 2% and a bottom surface 22. The shape of the insert is not criticalbut can ybe varied depending upon the particular bit on which it is usedand also on the mounting provided therefor on the bit.

The insert 1i? is formed of two different materials having differenthardness and wear resist-ant characteristics which are fus-ed orsintered together. in the drawing, two layers of `different hardnessmaterials are shown, `an vouter layer, identied by number Z4, beingformed of material which has predominantly wear resistantcharacteristics, such as wear grade tungsten carbide, and an innerlayer, identified by number 26, which is formed substantially within theouter layer and has shock resistant tungsten carbide. Shock resistanttungsten carbide, like wear resistant tungsten carbide is very hard butis less hard than the wear resistant carbide.

The actual construction of the insert may take place in any desired waysuch as by molding. When a mold is used the mold cavity is filled withthe several grades of tungsten carbide material in powder form. The weargrade material 24 which forms the outer layer is first poured into themold and distributed in the desired pattern such as the pattern shown inthe drawing. The inner layer is then formed by filling the mold cavitywith the shock material 26, also in powder form. Next, the mold isclosed and heat and pressure applied until the two grades are sintered.together to form the completed insert. A binder material (not shown) isalsopresent in the carbides to hold the carbide particles together. Theusual binder is cobalt. During the sintering operation some interchangeof the binder takes place between the different powder mixes and makesthe line of demarcation between the mixes indistinct. The interchange ofbinder ,and the sintering operation binds carbides together verystrongly.

When drilling with the insert 1d, initially only the wea-r grade ofcarbide is in contact with the drilled sur- A neocon face. Not untilconsiderable wear of the wear resist-ant carbide takes place will thecore or inner layer 26 emerge and make contact with the surface beingdrilled causing the insert to become more shock resist-ant. This is av-ery desir-able wear condition and prolongs the usable: life of theinsert.

A body .25 of a typical drill bit is shown in FIG. 6 having ya channel`shaped groove 27 therein for `an insert iii. The insert 16 ispositioned in the groove 27 with the cutting edge i2 extending outwardlytherefrom for engaging a surface to be drilled.

If desired, the body 2S of the drill bit can also be used to close themold cavity when the insert is formed. if this is done the insertforming materials are fused directly to the body of the bit. An exampleof this modied construction is shown in FIG. 5, wherein the bit body v2Shas two spaced cuttingrmembers 16a each formed of two layers 2da and 26aof hard material corresponding to layers: 24 and 26 respectively on theinsert 1i?. This modified construction reduces the ychance .of afracture occurring between Ithe insert .and the bit.

FiG. 7 is a cross-section view of the bit construction of FIG. andillustrates by the overlapping section lines the relatively indistinctconnections between the two grades of carbide material 24a and 26a andbetween the carbide materials and the bit body 28 itself.

FIGS. S40 illustrate a typical structure 30 in which a. bit .such as thebit oi' FiGS. 5-7 is made. The structure 3% has an opening 32 whichreceives and is closed by the body ZS of the bit, and the body 28 isshown being held in the opening by a tool 33 (FIG. 9). The body 23 canhave one or lmore grooves formed in the end thereof for receivinghardened portions, 'and for illustrative purposes the body shown in thedrawings has two such grooves. The 'structure 3i) `also has openings '34`and 36 associatedV with the ybody grooves into which particles of hardmaterials `are inserted during marking of the bit. The openings. y

34 and 35 in the structure shown receive tools such as tools 35.3 and i?which are used to pack land to give shape yto the particles. The tools3S and 40 may also be used to close the mold. The tool 38 as shown inFIG. 9 is used to form :and pack the inner layers of particles 26a, andthe tool 4,6 is -used form and pack the outer layers 24a. FIG. l0 lshows:a cross-section view through the mold structure and bit and illustratesa typical arrangement ci' the particles which is simil-ar Ito thearrangement of particles in the inserts of FIGS. 1-4. After .the hardmaterials .are packed in the mold structure the structure is subjectedto predetermined pressure and temperature to solidify the materials andto fuse the materials together `and to lthe body 28. The particular moldstructure 3b shown sand described herein illustrates one of many pos`sible structures that could be used to form the bit and is notint-ended to limit the invention to ,any one particular structure.Furthermore, it is contemplated to use a similar mold vstructure whenmaking the inserts of FIGS. l4.

One of the principal vadvantages obtained by forming an insert or drillbit in the manner taught by this invention is that it results in animproved wear pattern and a longer bit life. As already pointed out whena drill bit employing one or more of the present Iinserts is rst putinto service only the predominantly wear resistant materialmakes'contact with the material being drilled. As the insert wears awayits characteristics change from predominantly wear characteristics tomore predominantly shock characteristics. This change has certainadvantages in prolonging the life of the bit. One reason for this isthat the most efficient operation of a bit occurs during the rst fewuses thereof because closer to 100% of the number Vof bits are operatingand because these bits are in Itheir best cutting condition. In lthelast few uses, on the other hand, after the bits have been regroundseveral times and are of different sizes and shapes the number ofoperating bits may have dropped oir substantially. By having thepredominantly Wear resistant layer on the Iouter surface of the insert,the life of the insert is increased, particularly during the importantirst few uses, and furthermore a minimum amount of wear takes placeduring these important first few uses when the inserts are operating atmaximum efficiency.

Obviously, in forming the inserts, the thickness of the different gradescan be varied and lthe distribution of the different grades can beproportioned to meet diierent operating conditions. The presentinvention is not intended to be limited to particular quantities anddistribution or even to particular materials, and the drawings anddescription `are presented for illustrative purposes only.

Even -alter the insert has Worn down a substantial amount and the shockgrade tungsten carbide is exposed to the work, some of 'the wear grademafterialremains i around the periphery of the insert and in contactwith the surface being drilled. This also tends to further prolong thelife ofthe insert by preventing too rapid wear of the shock gradematerial.

' The present insert construction has the still further usual advantagesprovided by a composite insert formed by two or more grades of materialhaving diierent hardness and wear characteristics. These usualadvantages, however, are increased in the present device because of themanner in which the materials are fused together. This is particularlytrue with respect to the transmission of shocks encountered duringdrilling from the predomi-V nantly wear to the predominantly shockmaterials. Furthermore, as explained above the fusion of the two gradesproduced by the interchange of the binder during the sintering makes theline of demarcation between the grades less distinct and eliminateszones of potential fracture. The same is lalso true to some extent whenYthe inserts are attached directly to the bit by having the bit bodyclose the mold as described in connection with FIG. 5.

Thus it -is Aapparent that there has been provided lan insert for adrill bit, such as a rock drill bit, which lfulfills all of the objectsand advantages sought therefor. Obviously, many changes, modificationsand `alterations can be made lto the present .device by those skilled inthe art without departing from the spirit and scope of the invention.All such changes, modifications and alterations which do notv departfrom lthe spirit and scope of the invention are deemed covered by theinvention which is limited only by the claims which follow.

What is claimed:

' l. A drill bit comprising a bit body having a longitudinal axisextending between opposite ends of the body, Aone end of the body havinga pair of grooves, each groove disposed on opposite sides `of said axis,each groove having ea concave bottom surface extending outwardly rela-Vtive to the axis and sloping toward the other end of the body, an innernon-work engaging layer formed of carbide material in each groove andintegrally bonded to the concave surface in the groove, the sides ofeach inner ylayer spaced from the sides of its respective groove, theouter end of each inner layer spaced from the outer end of itsrespective groove, each inner layer having a con- Vex outer surfacespaced from said concave bottom surface, an outer exposed layer ofcarbide material in each groove occupying the remainder of the spacetherein not occupied by the inner layer and integrally bonded to thesurfaces of said groove and inner layer whereby each outer layercompletely encloses one of said inner layers, each outer layer having aportion projecting out of its respective groove and formed with acutting edge normal to said axis, the outer layers of carbide materialcharacterized by being hard .and having predominantly wear resistantproperties, each inner layer of carbide material being of ysubstantialhardness but less hard than the outer layers and having more resiliency:and toughness, a binder material integrally uniting said layers andsaid body.

2. A drill bit as defined in claim 1, wherein said binder materialincludes cobalt.

3. A drill bit as defined in claim l, wherein said outer 5 :layer has aradially outer end surface parallel to said axis.

References Cited in the le of this patent 6 Griflths Dec. 11, 1951Annesley Oct. 6, 1953 Cummins Nov. 9, 1954 Hoglund Feb. 21, 1956 Edstromet al June 19, 1956 Haglund et al. Ian. 15, 1957 Haglund June 2, 1959FOREIGN PATENTS Great Britain Mar. 29, 1950 France July 23, 1956

1. A DRILL BIT COMPRISING A BIT BODY HAVING A LONGITUDINAL AXISEXTENDING BETWEEN OPPOSITE ENDS OF THE BODY, ONE END OF THE BODY HAVINGA PAIR OF GROOVES, EACH GROOVE DISPOSED ON OPPOSITE SIDES OF SAID AXIS,EACH GROOVE HAVING A CONCAVE BOTTOM SURFACE EXTENDING OUTWARDLY RELATIVETO THE AXIS AND SLOPING TOWARD THE OTHER END OF THE BODY, AN INNERNON-WORK ENGAGING LAYER FORMED OF CARBIDE MATERIAL IN EACH GROOVE ANDINTEGRALLY BONDED TO THE CONCAVE SURFACE IN THE GROOVE, THE SIDES OFEACH INNER LAYER SPACED FROM THE SIDES OF ITS RESPECTIVE GROOVE, THEOUTER END OF EACH INNER LAYER SPACED FROM THE OUTER END OF ITSRESPECTIVE GROOVE, EACH INNER LAYER HAVING A CONVEX OUTER SURFACE SPACEDFROM SAID CONCAVE BOTTOM SURFACE, AN OUTER EXPOSED LAYER OF CARBIDEMATERIAL IN EACH GROOVE OCCUPYING THE REMAINDER OF THE SPACE THEREIN NOTOCCUPIED BY THE INNER LAYER AND INTEGRALLY BONDED TO THE SURFACES OFSAID GROOVE AND INNER LAYER WHEREBY EACH OUTER LAYER COMPLETELY ENCLOSESONE OF SAID INNER LAYERS, EACH OUTER LAYER HAVING A PORTION PROJECTINGOUT OF ITS RESPECTIVE GROOVE AND FORMED WITH A CUTTING EDGE NORMAL TOSAID AXIS, THE OUTER LAYERS OF CARBIDE MATERIAL CHARACTERIZED BY BEINGHARD AND HAVING PREDOMINANTLY WEAR RESISTANT PROPERTIES, EACH INNERLAYER OF CARBIDE MATERIAL BEING OF SUBSTANTIAL HARDNESS BUT LESS HARDTHAN THE OUTER LAYERS AND HAVING MORE RESILIENCY AND TOUGHNESS, A BINDERMATERIAL INTEGRALLY UNITING SAID LAYERS AND SAID BODY.